UBSAN: shift-out-of-bounds in __vcc_connect

Status: upstream: reported syz repro on 2026/08/26 12:18
Subsystems: net usb
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+f6ac161ee9699270b8dd@syzkaller.appspotmail.com
First crash: 5d23h, last: 5d19h
✨ AI Patch Versions (1)
Version Stage Reported Report Link Job
1 moderation 2026/08/26 16:47 Discussion 85f31c7a-29ad-45c0-a4e9-c74384abe250
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
85f31c7a patching UBSAN: shift-out-of-bounds in __vcc_connect 2026/08/26 14:13 2026/08/26 14:13 2026/08/26 16:47 a2b77b9e
bfed4161 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ UBSAN: shift-out-of-bounds in __vcc_connect 2026/08/23 00:00 2026/08/23 00:00 2026/08/23 00:58 1e72964b
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [net?] [usb?] UBSAN: shift-out-of-bounds in __vcc_connect 0 (2) 2026/08/26 13:35
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 UBSAN: shift-out-of-bounds in __vcc_connect origin:upstream -1 syz 2 10d 11d 0/3 upstream: reported syz repro on 2026/08/17 12:28
linux-6.1 UBSAN: shift-out-of-bounds in __vcc_connect origin:upstream -1 syz 2 14d 14d 0/3 upstream: reported syz repro on 2026/08/13 20:01
Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/08/26 13:35 42m kartikey406@gmail.com patch upstream OK job log log

Sample crash report:
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in net/atm/common.c:382:32
shift exponent -1 is negative
CPU: 0 UID: 0 PID: 5987 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:233
 __ubsan_handle_shift_out_of_bounds+0x36d/0x400 lib/ubsan.c:494
 __vcc_connect+0x14b4/0x19c0 net/atm/common.c:382
 vcc_connect+0x328/0x8f0 net/atm/common.c:498
 pvc_bind+0x272/0x380 net/atm/pvc.c:52
 __sys_bind_socket net/socket.c:1945 [inline]
 __sys_bind+0x2e3/0x410 net/socket.c:1976
 __do_sys_bind net/socket.c:1981 [inline]
 __se_sys_bind net/socket.c:1979 [inline]
 __x64_sys_bind+0x7a/0x90 net/socket.c:1979
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc16739e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff0c105ee8 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 00007fc167625fa0 RCX: 00007fc16739e0d9
RDX: 000000000000000c RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007fc167435024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc167625fac R14: 00007fc167625fa0 R15: 00007fc167625fa0
 </TASK>
---[ end trace ]---

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/22 18:08 upstream 26260251022f 1e72964b .config strace log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root UBSAN: shift-out-of-bounds in __vcc_connect
2026/08/22 14:29 upstream 26260251022f 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root UBSAN: shift-out-of-bounds in __vcc_connect
* Struck through repros no longer work on HEAD.